1. Field
The disclosed embodiments relate to a system for monitoring anemobaroclinometric parameters in an aircraft. This system can be used to obtain knowledge, on board the aircraft, of the value of the anemobaroclinometric parameters relative to the flight of the aircraft. Anemobaroclinometric parameters are the parameters related to the position and speed of the aircraft in flight relative to the surrounding air.
The disclosed embodiments can be applied in aeronautics and especially in the measurement of parameters pertaining to this anemoclinometry of the aircraft.
2. Brief Description
It is important, on board an aircraft, to have certain items of information on the flight of the aircraft. Anemometric measurements techniques are used to obtain this knowledge, relating especially to the airspeed of the aircraft, its position in space relative to the air, its altitude as well as direct air parameters. These items of information are called anemobaroclinometric parameters. These anemobaroclinometric parameters include parameters relative to the air surrounding the aircraft, such as the static pressure, the dynamic pressure or again the total air temperature. There are also parameters relative to the position of the aircraft in this environment such as the speed of the aircraft, its angle of attack or again in its side-slip angle. The angle of attack is the relative angle between the direction of airflow and the horizontal path of the aircraft. The side-slip angle of the aircraft is the angle of airflow relative to the path of the aircraft.
From the value of certain of these parameters, it is possible to determine the values of some other of these parameters. Thus, to know the value of all the anemobaroclinometric parameters that are useful on board the aircraft, certain of these anemobaroclinometric parameters are measured and the other parameters are deduced therefrom.
At present, the parameters are measured on board the aircraft by means of different probes placed outside the aircraft, on the external skin of the aircraft.
A classic system for the detection of anemobaroclinometric parameters in an aircraft is shown in FIG. 1. The system comprises a primary detection circuit and a secondary detection circuit, also called a standby circuit, used in the event of non-operation of the primary circuit or measurement problems detected on the primary circuit 1.
The primary circuit 1 comprises several measurement channels. Generally, the primary circuit comprises three substantially identical measurement channels 10, 20, 30. These three measurement channels 10, 20 and 30 all carry out a measurement of the same parameters. The existence of several measurement channels in a same circuit is aimed at providing for redundancy of the measurements for reasons of flight safety of the aircraft. It is thus ensured that the measurement obtained is accurate.
Classically, each measurement channel 10, 20 or 30 of the primary circuit 1 comprises:
one or more probes for the detection of the static pressure 13-14, 23-24 or 33-34,
a probe for the detection of the dynamic pressure, or total pressure,
a probe for the measurement of the total air temperature, and
a probe to measure the angle of attack of the aircraft.
In certain aircraft, several probes are assembled in one and the same probe which provides several values of parameters. In the case of FIG. 1, a multifunction probe MFP 15, 25, 35 measures the dynamic pressure, the total air temperature and the angle of attack.
On board certain aircraft, as in the example of FIG. 1, an SSA (side-slip angle) probe 11, 21, 31 is used to measure the side-slip angle of the aircraft.
For each measurement channel, the pieces of information measured by the different probes are transmitted to a data-processing device ADIRU 12, 22, 32. This data-processing device 12, 22, 32 processes the measurements made by the probes and determines the values of the other non-measured parameters. It carries out for example the determining of the computed airspeed, the true airspeed of the aircraft and the Mach number of the aircraft.
As explained here above, the classic monitoring systems comprise a first security level obtained by the redundancy of the measurements in the primary circuit 1. Generally, the classic monitoring systems comprise a second security level obtained by the secondary circuit 2. Classically, this secondary circuit 2 comprises one or more static pressure probes 43, 44 and one Pitot tube 40 which detects the dynamic pressure of the air. This secondary circuit 2 comprises one or more data-processing devices 41, 42 which process the values measured in order to deduce the non-measured anemobaroclinometric parameters therefrom.
Thus, in the event of failure of the primary circuit 1, the minimum information needed for the security of the flight of the aircraft is given by the secondary circuit 2.
As explained here above, the flight safety is provided, in classic systems for the monitoring of anemobaroclinometric parameters by the redundancy of the measurement channels in the primary circuit and by the existence of the secondary circuit. In other words, security is obtained by means of detection circuits that combine mechanics and electronics. These primary and secondary detection circuits are therefore circuits of a same mechanical and electronic type. Consequently, if a phenomenon is liable to prompt dysfunction in an element of the system, for example a static pressure probe, then all the similar elements of the system, i.e. all the static pressure probes, are also affected. There is then no way, anywhere in the system, of knowing the static pressure of the air.
Furthermore, the different probes used in classic systems are installed on the external skin of the aircraft, protruding out of said skin. In particular, the Pitot tube is a tube that extends beyond the aircraft and is placed in the direction of the forward progress of the aircraft. The static pressure probe requires an aperture in the wall of the fuselage, perpendicular to the direction of forward progress of the aircraft. The probes used to measure angle of attack and side-slip angle each have a mobile fin, mounted on a rotational axis, sensitive to the variation in airflow relative to the aircraft. These probes therefore constitute protuberant features on the external skin of the aircraft. They thus provide drag to the aircraft. Furthermore, they can generate noise.
Furthermore, these probes are sensitive to frost and rain. In order that frost may be prevented from getting deposited on it, a probe must be equipped with heating means: this increases the volume of the probe and hence the size of the protuberance on the external skin of the aircraft.